The vehicle tire has a tread with a function of establishing rolling contact with a foundation, such as a roadway. The tread is formed with a tread pattern featuring divergent grooves for providing the tread with tread blocks, i.e. the tread comprises blocks and grooves. The grooves have a purpose of enabling the water, possibly present on the foundation, to flow in a way to establish a contact as good and tight as possible between the tread, more specifically a tread block, and the roadway. The water present on the foundation is displaced by means of the grooves from under the tread blocks primarily sideways of the tire. Some of the water remains within confines of the grooves, whereby the tire rolls over the water in such a way that, at the rolling portion, the water runs along the grooves alongside the tread blocks past the rolling portion. Vehicle tires in road traffic service are legally required to have sufficiently deep grooves for the safe operation of a vehicle in fluctuating weather conditions.
The flow rate of water in a groove is naturally strongly dependent on the driving speed of a vehicle. The effect of grooves on the flow rate and volume flow of water is a significant factor in terms of contact between water and tire. In the event that the grooves are not able to displace a sufficient amount of water from the rolling portion, i.e. from the contact patch, the tire will climb onto the top of a water cushion present on the foundation for so-called aquaplaning, whereby the friction between tire and foundation disappears almost completely. Hence, it is an objective to provide such a design for the grooves that the flow of water in a groove is as efficient as possible.
In the prior art, the subject matter is discussed in EP 1614549, which discloses a tread pattern having a specific rotating direction and being vigorously divided by grooves into tread blocks, and being provided with transverse, inclined grooves which conduct water from the tread block area towards the circumferential grooves of the tire. Another teaching of the publication is that the intersection of inclined grooves and circumferential grooves can be provided with rounded edges.